global keyword and $GLOBALS usage in PHP

<span><span><?php<br>$a </span><span>= </span><span>1</span><span>; </span><span>/* <span>global</span> scope */<br></span><span>function </span><span>Test</span> <span>()<br>{<br> echo </span><span>$ this script will not have any output because The echo statement refers to a local version of the variable </span><span>$a</span><span>, and within this scope, it is not assigned a value. You may notice that PHP's global variables are a little different from C language. In C language, global variables automatically take effect in functions unless overridden by local variables. This may cause some problems, someone may accidentally change a global variable. Global variables in PHP must be declared as <br>global</span>. <span><br></span><span>global</span> Keyword <span><br>First, an example using </span><span>global</span></span>:

Example #1 Using

global

$a

= 1

;$b

=

2;

function

Sum<span>()<span>{<br> </span>global<span> </span><span>$a</span><span>, <br></span>$b<span></span>;<span> + </span><span>$b</span><span>;<br>}</span> <span></span>Sum<span><br>();<br>echo <span></span>$b</span><span>;</span><span></span>?> After global variables <span></span>$a<span><br> and </span><span>$b</span><span> are declared in a function, all references to either variable will point to its global version. PHP has no limit on the maximum number of global variables that a function can declare. </span><span>The second way to access variables in the global scope is to use special PHP customization </span><span>$GLOBALS </span><span>Array. The previous example could be written as: </span><span><br>Example #2 using <br></span>$GLOBALS <span></span>replacement<span>global<br></span><span></span><span><br></span><?php<span>$a </span></span>=

1

;

$b = 2 ;

function

Sum( ){

$GLOBALS['b'] =

$GLOBALS

[<span><span>'a'<br></span>] + <span></span>$GLOBALS<span></span> [<span><br>'b'</span><span> ];</span>}<span></span><span>Sum</span><span>();<br>echo </span><span>$b</span><span>;<br><br></span>?><span></span><span></span><span></span><span></span><span>$GLOBALS </span><span> is an associative array, each variable is an element, the key name corresponds to the variable name, and the value corresponds to the content of the variable. </span><span>$GLOBALS </span><span>Exists in the global scope because $GLOBALS is a superglobal variable. The following example shows the use of superglobal variables: </span><span></span>Example #3 Example demonstrating super global variables and scope <span></span><span></span><span><br><?php<br></span><span>function </span><span>test_<br>global</span><span></span>()<span>{<br>   </span><span>/ / Most of the predictions Defining variables is not "super", they need to use the 'global' keyword to make them available in the local scope of the function. </span> </span>

global

$HTTP_POST_VARS; echo $HTTP_POST_VARS[

'name'

];

// Superglobals are valid in any scope, they do not require 'global ' statement. Superglobals were introduced in PHP 4.1.0.       <span><span>echo <br></span>$_POST<span></span>[<span><span>'name'</span></span>];<span>}<br><br></span>?><span><br></span><span><span></span></span> <span> The above introduces the usage of the global keyword and $GLOBALS in PHP, including relevant content. I hope it will be helpful to friends who are interested in PHP tutorials. </span> <span> <br></span></span></span></span>